Battery Control System and Battery Control Method

ABSTRACT

When detecting a fault of a master control device, a slave control device refers to master-device-line information, and obtains line information to establish a connection with the other master control device. The slave control device transmits connection request information to the master control device extracted from the other master control devices. The other master control device determines whether or not it is connectable with the slave control device that has transmitted the connection request information, and transmits a determination result as connectability information. The slave control device switches a communication line to the other master control device when the received connectability information indicates the connectable status.

CROSS REFERENCE TO RELATED APPLICATION

This application is a divisional of U.S. application Ser. No.13/408,017, filed Feb. 29, 2012, which claims priority from JapanesePatent Application No. 2011-044039 filed on Mar. 1, 2011, thedisclosures of which are expressly incorporated by reference herein.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a battery control system and a batterycontrol method which dispose, as a hierarchical structure, controldevices that control batteries.

2. Description of the Related Art

A technology of charging a battery with power generated by utilizingnatural energy and with power from a system is getting attention. Abattery control system realized by such a technology has, as shown inFIG. 9, slave control devices 93 controlling a battery and connected inseries or in parallel as a group, and a master control device 92comprehensively controls such a group of the slave control devices 93.Moreover, a whole group of the plurality of master control devices 92 ismanaged by a battery-system managing device 91, and thus alarge-capacity battery is realized. In the battery control system havingmaster and slave control systems as a hierarchical structure, thebattery-system managing device 91 transmits a control signal to instructcharging, discharging, etc., of the battery to each slave control device93 through the master control device 92, and manages a status of acommunication line for transmitting/receiving the control signal and theoperation status of the control device itself (see JP 2000-358330 A).

According to the conventional battery control system shown in FIG. 9,however, when the master control device 92 suffers a fault like abreakdown, a communication with the slave control devices 93 managed bythat master control device 92 is disabled, and a batterycharging/discharging control is also disabled even if the batterycontrolled by that master and slave control devices 92 and 93 is in anormal condition.

For example, in the example case shown in FIG. 9, when a fault occurs atthe master control device 92 (92A), the slave control devices 93 ((1) to(8)) under the control of such a master control device become unable tocontrol the battery since a communication is disabled between the mastercontrol device 92 and each slave control device 93.

The present invention has been made in view of such a circumstance, andit is an object of the present invention to provide a battery controlsystem and a battery control method that can avoid uncontrollability ofa battery by slave control devices when a master control device suffersa fault in a system which establishes a hierarchical structure of themaster control system and the slave control systems and which transmitsa control signal for controlling a battery.

SUMMARY OF THE INVENTION

To address the above-explained technical issue, a battery control systemof the present invention causes a slave control device to refers tomaster-device line information when detecting a fault of a mastercontrol device, and obtains line information to establish a connectionwith the other master control device. Next, the slave control devicetransmits connection request information to the master control deviceextracted from the other master control devices. The other mastercontrol device determines whether or not a connection with the slavecontrol device that has transmitted the connection request informationis possible, and transmits a determination result as connectabilityinformation. The slave control device switches a communication line tothe other master control device when the received connectabilityinformation indicates a connectable status.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagram for explaining a process outline by a batterycontrol system according to an embodiment of the present invention;

FIG. 2 is a diagram showing an example connection (four series and twoparallel) of an electric system of a battery control module;

FIG. 3 is a diagram showing an example connection (eight series) of anelectric system of a battery control module;

FIG. 4 is a diagram showing an example connection (two series and fourparallel) of an electric system of a battery control module;

FIG. 5 is a functional block diagram showing example configurations of aslave control device, a master control device and a battery-systemmanaging device in the battery control system according to theembodiment of the present invention;

FIG. 6A is a diagram showing an illustrative data structure of stringinformation according to the embodiment of the present invention;

FIG. 6B is a diagram showing an illustrative data structure of stringinformation according to the embodiment of the present invention;

FIG. 7 is a flowchart showing a flow of a communication-line switchingprocess executed by the slave control device according to the embodimentof the present invention;

FIG. 8 is a sequence diagram showing a whole process flow by the batterycontrol system according to the embodiment of the present invention; and

FIG. 9 is a diagram for explaining a process outline of a batterycontrol system according to a prior art.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

<Process Outline>

First, an explanation will be given of a process outline executed by abattery control system 1 according to an embodiment of the presentinvention.

FIG. 1 is a diagram for explaining a process outline by the batterycontrol system 1 according to the embodiment.

As shown in FIG. 1, the battery control system 1 of this embodimentincludes a plurality of slave control devices 30 that controlcharging/discharging of a battery, a plurality of master control devices20 (20A, 20B, 20C, etc.,) each connected to the plurality of slavecontrol devices 30 via a communication line (a first communication line)5, and configured to control the whole plural slave control devices 30connected to the local master control device 20, and a battery-systemmanaging device 10 which is connected to the plurality of master controldevices 20 via a communication line (a second communication line) 6 andwhich controls the whole battery control system 1.

According to the prior art battery control system shown in FIG. 9, forexample, a master control device 92A and slave control devices 93 thatare the slave devices of the master control device are disposed as abattery pack 2 with a fixed communication line 5. Hence, when the mastercontrol device 92A suffers a fault, the slave control devices 93 ((1) to(8)) connected to the master control device 92A as slaves become unableto communicate, and thus a control of a battery, such as charging anddischarging, is disabled.

According to the battery control system 1 of this embodiment, as shownin FIG. 1, when, for example, the master control device 20A suffers afault, the slave control devices 30 that are the slave devices of themaster control device 20A transmit a connection request (connectionrequest information to be discussed later) to the other master controldevice 20 (e.g., master control devices 20B and 20C) other than thebreakdown master control device 20A. Next, when the other master controldevice 20 (20B and 20C) is connectable, those slave control devices 30switch the communication line (the first communication line) 5, andcharge/discharge the battery under the control of the other mastercontrol device 20 (20B and 20C).

Moreover, the slave control device 30 switches of this embodiment, foreach string indicating a configuration (a group) of series connection ofa set electric system, a communication line to the other master controldevice 20 of the same string. An explanation will now be given of astring (a group of series connection) according to this embodiment.

FIG. 2 is a diagram showing an example connection (four series and twoparallel) of an electric system of a battery module.

In this embodiment, a battery module means a configuration including theslave control devices 30 and a battery controlled by the slave controldevices 30. Illustration of the battery is omitted in FIGS. 2 to 4.

In FIG. 2, the slave control devices 30 (1) to (4) and 30 (5) to (8) areconnected in series, respectively, and such two systems are connected inparallel. The slave control devices 30 (1) to (4) or (5) to (8) inseries connection, respectively, are defined as a string (a group ofseries connection). The battery controlled by the slave control devices30 (1) to (4) and the battery controlled by the slave control devices 30(5) to (8) are connected in series, and groups of batteries in seriesconnection are connected in parallel. The communication line 5 fortransmitting/receiving control information, etc., with the mastercontrol device 20 is connected in parallel for each slave control device30.

According to the example case shown in FIG. 3 (eight series), the slavecontrol devices 30 (1) to (8) are connected in series, and configure astring. That is, batteries controlled by the slave control devices 30(1) to (8) are connected in series.

According to the example case shown in FIG. 4 (two series and fourparallel), the slave control devices 30 (1) and (2), (3) and (4), (5)and (6), (7) and (8) are connected in series, respectively and eachseries connection configures a string. That is, batteries controlled byrespective pairs of slave control devices 30 (1) and (2), (3) and (4),(5) and (6), (7) and (8) are connected in series, and groups of thebatteries in series connection are connected in parallel.

The reason why such a string (a group of series connection) isintroduced is if the slave control devices 30 belonging to the samestring detect a fault of the master control device 20 connected to thoseslave control devices 30, and switch the line individually, those slavecontrol devices 30 are connected to the other master control devices 20,respectively, and become uncontrollable. The introduction of the conceptof string is to prevent such uncontrollability. For example, in FIG. 1,when the slave control device 30 (1) which is controlled by the mastercontrol device 20A having a fault and belonging to the same string, andwhich switches the communication line to be connected to the mastercontrol device 20B, and the slave control device 30 (2) belonging to thesame string switches the communication line to be connected to themaster control device 20C, separate instructions for charging anddischarging are given from respective master control devices 20 (20B and20C) to the batteries in a series connection at different timings, andthe slave control devices 30 become uncontrollable.

The slave control device 30 of this embodiment stores in advanceinformation on the local string, and transmits a connection request(“connection request information” to be discussed later) containinginformation on the local string to the other master control device 20.Accordingly, the slave control devices 30 belonging to the same stringcan switch the communication line to the same other master controldevice 20. That is, the slave control devices 30 can switch thecommunication line to the other master control device 20 whilemaintaining the string (the group of series connection). The detail ofthis operation will be explained later.

<System Configuration>

Next, a detailed explanation will be given of individual configurationsof the slave control device 30, the master control device 20, and thebattery-system managing device 10 configuring the battery control system1 of this embodiment.

FIG. 5 is a functional block diagram showing respective configurationsof the slave control device 30, the master control device 20, and thebattery-system managing device 10 of the battery control system 1 ofthis embodiment.

<Slave Control Device>

First, an explanation will be given of the detail of a configuration ofthe slave control device 30 according to this embodiment.

The slave control device 30 controls charging/discharging of a battery 4under the control of the master control device 20. Moreover, the slavecontrol device 30 executes a process of switching the communication line5 to the other master control device 20 when the master control device20 connected to this slave control device 30 suffers a fault like abreakdown.

As shown in FIG. 5, the slave control device 30 includes a control unit31, a communication unit 32, and a memory unit 33.

The control unit 31 is responsible for the whole control of the slavecontrol device 30 which performs processes of charging/discharging thebattery 4 and switching a communication line to the other master controldevice 20, and includes a transmitting/receiving unit 311, a faultmonitoring unit 312, a master-device searching unit 313, aconnection-request-information generating unit 314, a connectabilityinformation obtaining unit 315, a line switching unit 316, and a batterycontrol unit 317.

The transmitting/receiving unit 311 controls transmission/reception ofinformation with the master control device 20 through the communicationunit 32.

The fault monitoring unit 312 receives a connection check signal fromthe master control device 20 at a predetermined interval, and transmitsa reply signal to the master control device 20, thereby periodicallymonitoring the communication line with the master control device 20.

When not receiving the connection check signal from the master controldevice 20 even if the predetermined interval has elapsed, the faultmonitoring unit 312 detects a fault occurring on the master controldevice 20, and transmits information on that fault to the master-devicesearching unit 313.

Moreover, after detecting that the fault has occurred on the mastercontrol device 20, when receiving the connection check signal again fromthat master control device 20, the fault monitoring unit 312 determinesthat the master control device 20 is recovered from the fault, andtransmits information on that recovery to the master-device searchingunit 313.

The master-device searching unit 313 refers to string information 300stored in the memory unit 33 when obtaining the information to theeffect that the fault occurring on the master control device 20 isdetected from the fault monitoring unit 312, and obtains information onthe slave control devices 30 configuring the local string (the group ofseries connection).

FIGS. 6A and 6B are diagrams showing an illustrative data structure ofthe string information 300 according to this embodiment.

FIG. 6A shows the string information 300 stored in the memory unit 33 ofthe slave control device 30 belonging to a string “A-1” under thecontrol of the master control device 20A in FIG. 1. Moreover, FIG. 6Bshows the string information 300 stored in the memory unit 33 of theslave control device 30 belonging to a string “A-2” under the control ofthe master control device 20A in FIG. 1.

As shown in FIG. 6A, the string information 300 of this embodimentincludes a master-device ID 301, a string ID 302, and a slave-device ID303.

The master-device ID 301 is unique to the master control device 20 towhich the slave control device 30 is currently connected. For example,the master-device ID 301 that is “A” of the master control device 20 isstored.

The string ID 302 is unique to the string (the group of seriesconnection) to which the slave control device 30 belongs. For example,the string ID 302 that is “A-1” of the string connected to the mastercontrol device 20A is stored. The string ID “A-1” indicates that thestring is set as the “first” string of the master control device 20A.

The slave-device ID 303 is unique to the slave control device 30, andfor example, the slave-device ID 303 that is “A-1-1” is stored. Theslave-device ID “A-1-1” indicates that, as an initial basic setting,this slave control device 30 is under the control of the master controldevice 20A, and is set as the “first” slave control device 30 among theslave control devices 30 with the string ID of “A-1”.

The string information 300 shown in FIG. 6A includes four records, andindicates that the four slave control devices 30 belong to the stringhaving the string ID 302 of “A-1”.

Likewise, the string information 300 shown in FIG. 6B indicates that thefour slave control devices 30 belong to the string having the string ID302 of “A-2” and connected to the master control device 20A.

Returning to FIG. 5, the master-device searching unit 313 refers to thestring information 300, and obtains the local slave-device ID 303 andinformation on the number of slave control devices 30 belonging to thelocal string.

Moreover, the master-device searching unit 313 refers tomaster-device-line information 350 stored in the memory unit 33, anddetermines whether or not line information (a frequency, a time slot, aphase, and a modulation scheme) necessary for a communication with eachmaster control device 20 is stored.

Next, when the stored master-device-line information 350 contains theline information of the other master control device 20, themaster-device searching unit 313 obtains the line information of theother master control device 20 from the master-device-line information350.

Moreover, when the master-device-line information 350 stored in thememory unit 33 does not contain the line information of the other mastercontrol device 20, the master-device searching unit 313 calculates theline information of the other master control device based on the lineinformation of the local master control device 20. For example, themaster-device searching unit 313 calculates and obtains the lineinformation of the other master control device 20 for each predetermineddifference in frequency within a predetermined frequency range set inadvance.

Next, the master-device searching unit 313 extracts a piece of lineinformation among the pieces of obtained line information of the othermaster control devices 20, and passes the extracted line information ofthe other master control device 20, the local slave-device ID 303obtained from the string information 300 and information on the numberof slave control devices 30 in the local string to theconnection-request-information generating unit 314 to execute acommunication line switching process for switching the communicationline 5 to the other master control device 20. The communication lineswitching process is a successive process executed by the master-devicesearching unit 313, the connection-request-information generating unit314, the connectability information obtaining unit 315, and the lineswitching unit 316, and will be explained in more detail later withreference to FIG. 7.

Next, the connection-request-information generating unit 314 generatesconnection request information containing the local slave-device ID 303obtained from the master-device searching unit 313 and the informationon the number of slave control devices belonging to the local string.Thereafter, the connection request information is transmitted to theextracted other master control device 20 based on the line informationof the other master control device 20 extracted by the master-devicesearching unit 313.

The connectability information obtaining unit 315 obtains connectabilityinformation from the other master control device 20 which has receivedthe connection request information. The connectability informationindicates whether or not the slave control devices 30 by whatcorresponds to the number thereof configuring the local string areconnectable to the other master control device 20, and is added withinformation “connectable” or “unconnectable”.

When the information added to the connectability information is“connectable”, the connectability information obtaining unit 315 passessuch information to the line switching unit 316.

Conversely, when the information added to the connectability informationis “unconnectable”, the connectability information obtaining unit 315passes such information to the master-device searching unit 313.

The line switching unit 316 switches the communication line 5 to theother master control device 20 which has transmitted the connectabilityinformation of “connectable” when obtaining the information of“connectable” from the connectability information obtaining unit 315.

Moreover, the line switching unit 316 switches the communication line 5to the original master control device 20 when obtaining information tothe effect that the original master control device 20 is recovered fromthe fault from the fault monitoring unit 312.

The battery control unit 317 receives a battery control signal from thebattery-system managing device 10 via the master control device 20, andcontrols charging/discharging of the battery 4 connected to the batterycontrol unit 317.

The communication unit 32 includes a communication interface fortransmitting and receiving information with each master control device20.

The memory unit 33 includes memory means, such as a flash memory or aRAM (Random Access Memory), and stores the string information 300, themaster-device-line information 350, etc.

The function of the control unit 31 of the slave control device 30 isrealized by, for example, a CPU (Central Processing Unit) which extractsin a memory like a RAM a program stored in the memory unit 33 of theslave control device 30 and runs such a program, or an exclusivecircuit, etc.

<Master Control Device>

Next, a detailed explanation will be given of a configuration of themaster control device 20 according to this embodiment.

The master control device 20 is connected to the battery-system managingdevice 10 and individual local slave control devices 30, and transmitscontrol information from the battery-system managing device 10 to eachslave control device 30.

As shown in FIG. 5, the master control device 20 includes a control unit21, a communication unit 22, and a memory unit 23.

The control unit 21 is responsible for the control of the whole mastercontrol device 20, and includes a transmitting/receiving unit 211, afault monitoring unit 212, a slave-device connection managing unit 213,and a battery control unit 214.

The transmitting/receiving unit 211 controls transmission and receptionof information with the battery-system managing device 10 and each slavecontrol device 30 via the communication unit 22.

The fault monitoring unit 212 receives a connection check signal fromthe battery-system managing device 10 at a predetermined interval, andtransmits a reply signal to the battery-system managing device 10,thereby periodically monitoring the communication line with thebattery-system managing device 10. Moreover, the fault monitoring unit212 transmits a connection check signal to each slave control device 30at a predetermined interval, and receives a reply signal from each slavecontrol device 30, thereby periodically monitoring the communicationline with each slave control device 30.

The slave-device connection managing unit 213 executes a followingprocess when receiving the connection request signal from theslave-control device 30 under the control of the other master controldevice 20 than the local master control device 20 via thetransmitting/receiving unit 211. That is, the slave-device connectionmanaging unit 213 determines whether or not the local master controldevice 20 is connectable as the other master control device 20 to theslave control devices 30 by what corresponds to the number of slavecontrol devices 30 belonging to the string where the slave controldevice 30 which has requested a connection belongs based on theinformation which is added with the connection request signal and whichis on the number of the slave devices 30 belonging to the string wherethe slave control device 30 that has requested a connection belongs.

The determination by the slave-device connection managing unit 213 forthe connectability can be made based on a determination on whether ornot the transmission channels within the frequency range set for themaster control device 20 have unused channels by what corresponds to thenumber of slave control devices 30 belonging to the string where theslave control device 30 which has requested a connection belongs when,for example, transmission is carried out through a frequency divisionmultiplex scheme over the communication line 5, and whether or not timeslots have unused time slots by what corresponds to the number of suchslave control devices 30 belonging to the string when transmission iscarried out through a time division multiplex scheme, etc.

When determining that the slave control devices 30 by what correspondsto the number of slave control devices 30 belonging to the string areconnectable, the slave-device connection managing unit 213 replies theconnectability information added with the information “connectable” tothe slave control device 30 that has transmitted the connection requestinformation.

Conversely, when determining that it is unconnectable, the slave-deviceconnection managing unit 213 replies the connectability informationadded with the information “unconnectable” to the slave control device30 that has transmitted the connection request information.

The slave-device connection managing unit 213 receives the sameconnectability information from the slave control devices 30 belongingto the same string by what corresponds to the number of such slavecontrol devices 30, but transmits the same determination result on thedetermination of “connectable” or “unconnectable” as the connectabilityinformation to each slave control device 30.

Moreover, when each slave control device 30 which has received theconnectability information added with the information “connectable”switches the communication line, the slave-device connection managingunit 213 generates slave-device connection information 200 indicatingthat this slave control device 30 is connected to the local mastercontrol device 20, and stores the generated information in the memoryunit 23. Furthermore, the slave-device connection managing unit 213transmits the generated slave-device connection information 200 to thebattery-system managing device 10 via the transmitting/receiving unit211.

The battery control unit 214 transmits battery control informationreceived from the battery-system managing device 10 to the slave controldevice 30 connected to the local master control device 20.

The communication unit 22 includes a communication interface fortransmitting and receiving information with each slave control device 30and the battery-system managing device 10.

The memory unit 23 includes memory means, such as a flash memory or aRAM, and stores the slave-device connection information 200, etc.,indicating each slave control device 30 connected to the local mastercontrol device 20.

The function of the control unit 21 of the master control device 20 isrealized by, for example, a CPU (Central Processing Unit) which extractsin a memory like a RAM a program stored in the memory unit 23 of themaster control device 20 and runs such a program, or an exclusivecircuit, etc.

<Battery-System Managing Device>

Next, a configuration of the battery-system managing device 10 of thisembodiment will be explained in detail.

The battery-system managing device 10 is connected to each mastercontrol device 20, and transmits battery control information, etc., tothe slave control devices 30 under the control of each master controldevice 20.

As shown in FIG. 5, the battery-system managing device 10 includes acontrol unit 11, a communication unit 12, a memory unit 13, and aninput/output unit 14.

The communication unit 12 includes a communication interface fortransmitting and receiving information with each master control device20.

The memory unit 13 includes memory means, such as a hard disk, a flashmemory, or a RAM, and stores connection status information 100indicating to which slave control devices 30 each master control device20 connected to the battery-system managing device 10 is connected, etc.

The input/output unit 14 includes an input device (unillustrated), suchas a keyboard or a mouse, an output device (unillustrated) like adisplay, and an input/output interface for exchanging information withthose devices.

The control unit 11 is responsible for the control of the wholebattery-system managing device 10, and includes a transmitting/receivingunit 111, a fault monitoring unit 112, a connection status managing unit113, a battery managing unit 114, and a display processing unit 115.

The transmitting/receiving unit 111 controls transmission and receptionof information with each master control device 20 via the communicationunit 12.

The fault monitoring unit 112 transmits the connection check signal toeach master control device 20 at a predetermined interval, and receivesthe reply signal from each master control device 20, therebyperiodically monitoring the communication line with each master controldevice 20.

When not receiving the reply signal from the master control device 20even if a predetermined interval has elapsed, the fault monitoring unit112 detects the fault occurring on the master control device 20, andpasses information on that fault to the display processing unit 115.

Moreover, after detecting the fault occurring on the master controldevice 20, when receiving the reply signal from that master controldevice 20 again, the fault monitoring unit 112 determines that themaster control device 20 is recovered from the fault, and passesinformation on that recovery to the display processing unit 115.

The connection status managing unit 113 receives, from each mastercontrol device 20, the slave-device connection information 200indicating the slave control devices 30 connected to that master controldevice 20, and updates the connection status information 100 stored inthe memory unit 13.

Moreover, the connection status managing unit 113 passes theslave-device connection information 200 to the display processing unit115 when receiving such information from each master control device 20.

The battery managing unit 114 refers to the connection statusinformation 100 stored in the memory unit 13, and transmits batterycontrol information, etc., to the slave control devices 30 under thecontrol of each master control device 20.

The display processing unit 115 causes the unillustrated display deviceto display fault information indicating the fault master control device20 and obtained from the fault monitoring unit 112 and fault recoveryinformation. Moreover, the display processing unit 115 causes theunillustrated display device to display information on the slave controldevices 30 connected to each master control device 20 based on theslave-device connection information 200 received from the connectionstatus managing unit 113.

<Process Detail>

Next, a detailed explanation will be given of a communication-lineswitching process executed by the slave control device 30 according tothis embodiment. Thereafter, the flow of the whole process by thebattery control system 1 of this embodiment will be explained.

<Communication-Line Switching Process>

FIG. 7 is a flowchart showing a flow of the communication-line switchingprocess executed by the slave control device 30 of this embodiment. Thecommunication-line switching process causes the slave control device 30to switch the communication line to the other master control device 20when the master control device 20 becomes uncommunicatable due to afault like a breakdown. It is presumed that, as shown in FIG. 1, themaster control device 20A suffers a fault like a breakdown. The mastercontrol device 20A controls the slave control devices 30 ((1) to (8)) ofthe electric system in the four series and two parallel connection asshown in FIG. 2, and as shown in FIG. 1, the slave control devices 30((1) to (4)) belong to the string “A-1”, and the slave control devices30 ((5) to (8)) belong to the string “A-2”.

First, the fault monitoring unit 312 of the slave control device 30detects, upon checking of no check signal after the predeterminedinterval has elapsed with the master control device 20, that the mastercontrol device 20 is suffering a fault (step S101).

Next, the master-device searching unit 313 of the slave control device30 refers to the string information 300 stored in the memory unit 33,and obtains information on the slave control devices 30 configuring thestring where the local slave control device 30 belongs (step S102). Inthis step, the master-device searching unit 313 obtains, from the stringinformation 300, the slave-device ID 303 of the local device that is“A-1-1”, and information to the effect that the number of slave controldevices 30 belonging to the same string is four (see FIG. 6A).

Subsequently, the master-device searching unit 313 refers to themaster-device-line information 350 stored in the memory unit 33, anddetermines whether or not line information (frequency, time slot, phase,and modulation scheme) necessary to communication with the other mastercontrol device 20 is stored (step S103).

When the master-device-line information 350 is recorded with thenecessary line information to communicate with the other master controldevice 20 (step S103: YES), the master-device searching unit 313 obtainsthe line information for the other master control device 20 from themaster-device-line information 350 (step S104), and the processprogresses to next step S106.

Conversely, when the master-device-line information 350 is not recordedwith such necessary line information to communicate with the othermaster control device 20 (step S103: NO), the master-device searchingunit 313 calculates the line information of the other master controldevice 20 (step S105), and the process progresses to the next step S106.The calculation of the line information of the other master controldevice 20 by the master-device searching unit 313 is carried out by, forexample, calculating the line information of each master control device20 based on a predetermined difference in frequency stored in advance inthe memory unit 23 and within a frequency range used to communicate withthe master control device 20.

Next, in the step S106, the master-device searching unit 313 extractsone of the other master control devices 20 than the local master controldevice 20, and obtains the line information of the extracted mastercontrol device 20.

Regarding the extraction of the other master control device 20 by themaster-device searching unit 313, the same logic is applied to each ofthe slave control devices 30 (four devices) belonging to the same stringshown in FIG. 1 and one of the other master control devices 20 isextracted in the same order. Moreover, the way of extracting the mastercontrol device 20 by the master-device searching unit 313 may employ,for example, a logic of extracting the other master control device 20 inthe order of closer frequency to that of the master control device 20that has been connected before. Hence, the master-device searching units313 of the slave control devices 30 (four devices) belonging to the samestring do not separately extract the different master control devices20, but extract the same master control device 20 in accordance with thesame logic.

Subsequently, the connection-request-information generating unit 314 ofthe slave control device 30 generates the connection request informationincluding the slave-device ID 303 (A-1-1) of the local slave device 30obtained in the step S102, and the information on the number of slavecontrol devices 30 (four devices) configuring the local string (A-1).Thereafter, the connection-request-information generating unit 314transmits the generated connection request information to the othermaster control device 20 (e.g., the master control device 20B) based onthe line information of the other master control device 20 obtained inthe step S106 (step S107).

The connectability information obtaining unit 315 of the slave controldevice 30 obtains the connectability information added with informationon whether or not the master control device 20 is connectable from themaster control device 20 which has transmitted the connection requestinformation in the step S107 (step S108), and checks whether or not itis connectable (step S109).

When the information added to the connectability information indicates aconnectable status (step S109: YES), the connectability informationobtaining unit 315 passes such information to the line switching unit316, and the line switching unit 316 switches the communication line fora battery control to the connectable master control device 20 (stepS110).

Conversely, when the information added to the connectability informationindicates an unconnectable status (step S109: NO), the connectabilityinformation obtaining unit 315 passes such information to themaster-device searching unit 313, and the master-device searching unit313 determines whether or not all pieces of line information of theother master control devices 20 are processed (step S111).

The determination by the slave-device connection managing unit 213 ofthe master control device 20 on whether or not it is connectable is todetermine whether or not the slave control devices 30 by whatcorresponds to the number thereof in the string are connectable.Accordingly, the pieces of connectability information from the slavecontrol devices 30 (four devices) belonging to the same string are addedwith the same determination result “connectable” or “unconnectable”.Moreover, when the slave-device connection managing unit 213 isconfigured to determine whether or not the slave control device 30belonging to a string is connectable for the pieces of connectionrequest information from the slave control devices 30 (four devices)belonging to the same string, the further determination for the piecesof connection request information from the slave control devices 30 (theremaining three devices) belonging to the same string is unnecessary,and it is fine if the connectability information generated using thedetermination result of the first process is transmitted.

When there is the line information of the other master control device 20not processed yet (step S111: NO), the process returns to the step S106,and the master-device searching unit 313 extracts the next mastercontrol device 20.

Conversely, when determining that all pieces of line information of theother master control devices 20 are processed (step S111: YES), themaster-device searching unit 313 determines that the line switching isunavailable, and terminates the process (step S112).

In the example case shown in FIG. 1, as a result of the communicationline switching process, the four slave control devices 30 ((1) to (4))belonging to the string “A-1” switch the communication line 5 to themaster control device 20B, and the four slave control devices 30 ((5) to(8)) belonging to the string “A-2” switch the communication line 5 tothe master control device 20C.

According to such a process, each slave control device 30 can switch thecommunication line to the other master control device 20 whilemaintaining the string (the group of series connection).

<Whole Process by Battery Control System>

Next, an explanation will be given of a flow of the whole process by thebattery control system 1 of this embodiment.

FIG. 8 is a sequence diagram showing a flow of the whole process by thebattery control system 1 according to this embodiment.

It is presumed that as shown in FIG. 1 the master control device 20(20A) suffers a fault like a breakdown, the slave control devices 30(hereinafter, referred to as “slave control devices 30 a”) belonging tothe string “A-1” under the control of the master control device 20A andthe slave control devices 30 (hereinafter, referred to as “slave controldevices 30 b”) belonging to the string “A-2” also under the control ofthe master control device 20A perform line switching to be connected tothe other master control devices 20 (20B and 20C), respectively.

First, periodical monitoring is performed between the master controldevice 20A and the slave control device 30 a and the slave controldevice 30 b under the control of such master control device 20A, andbetween the master control device 20A and the battery-system managingdevice 10 (step S1). The four slave control devices 30 a and the fourslave control devices 30 b shown in FIG. 1 respectively performperiodical monitoring with the master control device 20A. The processesexecuted by the slave control device 30 a and the slave control device30 b and explained below are executed by respective four devices.

Respective fault monitoring units 312 of the slave control devices 30 aand 30 b detect that the master control device 20A is suffering a faultlike a breakdown since, for example, no connection check signal from themaster control device 20A is confirmed even after the predeterminedinterval (step S2: detect fault).

Moreover, the battery-system managing device 10 (the fault monitoringunit 122) detects that the master control device 20A is suffering afault since, for example, no reply signal to the connection check signaltransmitted by battery-system managing device 10 to the master controldevice 20A is confirmed even after the predetermined interval, anddisplays information on the fault detection on the display device(unillustrated) through the display processing unit 115 (step S3:display fault occurrence).

The slave control device 30 a that has detected the fault executes thecommunication-line switching process (see FIG. 7). The slave controldevice 30 a searches the other master control device 20 (step S4), andtransmits the connection request information to the searched mastercontrol device 20B (step S5). The master control device 20B determinesthat the four slave control devices 30 belonging to the string “A-1”(see FIG. 6A) are connectable, and transmits the connectabilityinformation indicating the determination result “connectable” to theslave control device 30 a (step S6). Next, the slave control device 30 aswitches the communication line for battery control from the mastercontrol device 20A to the master control device 20B (step S7). Next, themaster control device 20B transmits the slave-device connectioninformation 200 to the effect that the communication line is establishedwith the slave control devices 30 a (the four devices) belonging to thestring “A-1” to the battery-system managing device 10 (step S8).

The slave control device 30 b also detecting the fault executes the sameprocess as that of the slave control device 30 a (steps S4 to S8) withthe master control device 20C extracted from the other master controldevices 20 (steps S9 to S13).

The battery-system managing device 10 that has received respectiveslave-device connection information 200 from the master control device20B and the master control device 20C causes the display device todisplay information to the effect that the group of slave controldevices 30 belonging to the string “A-1” and the group of slave controldevices 30 belonging to the string “A-2” are connected to the mastercontrol device 20B and the master control device 20C, respectively (stepS14: display connection status).

Next, when the master control device 20A suffering a fault is recoveredfrom such a fault by repair, replacement, etc., respective faultmonitoring units 312 of the slave control devices 30 a and 30 b detectthat the master control device 20A is recovered from the fault by, forexample, receiving the connection check signal from the master controldevice 20A (step S21: detect fault recovery).

Moreover, the battery-system managing device 10 (the fault monitoringunit 122) detects that the master control device 20A is recovered fromthe fault by, for example, receiving the reply signal to the connectioncheck signal transmitted by the battery-system managing device 10 to themaster control device 20A within a predetermined interval, and causesthe display device to display information on the recovery from the faultthrough the display processing unit 115 (step S22: display faultrecovery).

Next, the slave control device 30 a that has detected the recovery ofthe master control device 20A from the fault switches the communicationline for a battery control from the master control device 20B to themaster control device 20A (step S23). Moreover, the slave control device30 b that has detected the recovery of the master control device 20Afrom the fault switches the communication line for a battery controlfrom the master control device 20C to the master control device 20A(step S24).

Subsequently, the master control device 20A transmits the slave-deviceconnection information 200 to the effect that the communication linesare established with the group of slave control devices 30 belonging tothe string “A-1” and the group of slave control devices 30 belonging tothe string “A-2” to the battery-system managing device 10 (step S25).

Next, the battery-system managing device 10 that has received theslave-device connection information 200 from the master control device20A causes the display device to display information to the effect thatthe master control device 20A is recovered from the fault and thecommunication line is returned to the original connection (step S26:display connection status).

As explained above, according to the battery control system 1 and thebattery control method according to this embodiment, even if the mastercontrol device 20 suffers a fault, the slave control device 30 under thecontrol of that master control device 20 can switch the line to theother master control device 20 while maintaining the string (the groupof series connection) where the local slave control device 30 belongs.Accordingly, it becomes possible to avoid uncontrollability of thebattery controlled by the slave control device 30 under the control ofthe master control device 20 suffering a fault.

The distributed processing of the battery control employed by thebattery control system 1 and the battery control method of thisembodiment is advantageous when the number of batteries is large, and isespecially advantages for the battery management of a natural energypower generating system in a mega-watt class.

What is claimed is:
 1. A method for controlling a battery system, the battery system comprising: a plurality of battery modules, each of which has a battery and a slave control device; a master control device connected to the plurality of slave control devices via a first communication line; and a battery system managing device connected to the plurality of master control devices via a second communication line, wherein the slave control devices configure a string for battery modules connected in series, and wherein if the master control device to which the slave control device is connected suffers a fault, the slave control device and other slave control devices belonging to the same string are connected to the same other master control device.
 2. The method of claim 1, wherein the master control device determines whether or not the master control device is connectable to all of the slave control devices belonging to the same string, and if connectable, the master control device is connected to all of the slave control devices belonging to the same string.
 3. The method of claim 1, wherein the master control device determines whether or not the master control device is connectable to all of the slave control devices belonging to the same string, and if not connectable, the slave control device searches other connectable master control device.
 4. The method of claim 2, wherein the master control device determines whether or not the master control device is connectable to all of the slave control devices belonging to the same string, and if not connectable, the slave control device searches other connectable master control device. 